A previous study of the epidemiology of subsite colon cancer in the Pittsburgh SMSA was based on the Third National Cancer Survey. Individuals with carcinoma of the ascending colon were noted to have a higher prevalence of prior cholecystectomy than individuals with carcinoma of the other sites within the colon. The information was only obtained by review of hospital records. We propose to determine the relationship between cholecystectomy and right sided colon cancer by doing a case control study. Cases of right sided colon cancer and controls consisting of carcinoma of the Sigmoid and descending colon will be identified by reviewing hospital records and interviews. A living neighborhood control will also be interviewed.